1. Field of the Invention
The present invention relates generally to antennas, and more specifically to small antenna structures possessing diversity characteristics.
2. Discussion of the Related Art
A multipath environment is created when radio frequency (RF) signals propagate over more than one path from the transmitter to the receiver. Alternate paths with different propagation times are created when the RF signal reflects from objects that are displaced from the direct path. The direct and alternate path signals sum at the receiver antenna to cause constructive and destructive interference, which have peaks and nulls. When the receiver antenna is positioned in a null, received signal strength drops and the communication channel is degraded or lost. The reflected signals may experience a change in polarization relative to the direct path signal. This multipath environment is typical of indoor and in-office wireless local area networks (WLAN).
An approach to addressing the multipath problem is to employ multiple receiver antenna elements in order to selectively receive a signal from more than one direction. This approach, known as xe2x80x9cdiversityxe2x80x9d, is achieved when receiving signals at different points in space or receiving signals with different polarization. Performance is further enhanced by isolating the separate antennas. Wireless communication link bit error rate (BER) performance is improved in a multipath environment if receive and/or transmit diversity is used.
Conventional antenna structures that employ diversity techniques tend to be expensive and physically large structures that utilize bulky connectors, such as coaxial cable connectors. Such antenna structures are not suitable for residential and office use where low-cost and small physical size are highly desirable characteristics. Thus, there is a need for an antenna structure capable of employing diversity techniques that overcomes these and other disadvantages.
The present invention advantageously addresses the needs above as well as other needs by providing a diversity antenna structure that includes a dome having a plurality of facets and a plurality of antenna elements. At least one facet has located thereon at least one antenna element.
In one embodiment, the invention can be characterized as an antenna structure that includes a dome having at least two non-coplanar facets, at least two antenna elements, and active circuitry attached to a first inner surface of the dome and coupled to the antenna elements. Each facet has located thereon one of the antenna elements.
In another embodiment, the invention can be characterized as a method of making an antenna structure. The method includes the steps of: forming a dome having a plurality of facets; mounting separate antenna elements on at least two of the facets; attaching active circuitry to a first inner surface of the dome; and coupling the active circuitry to the antenna elements.
In another embodiment, the invention can be characterized as a method of receiving a signal in a multi-path environment. The method includes the steps of: placing a dome having a plurality of facets in the multi-path environment; receiving the signal from a first direction in the multi-path environment with a first antenna element located on one of the facets of the dome; and receiving the signal from a second direction in the multi-path environment with a second antenna element located on another of the facets of the dome.
In another embodiment, the invention can be characterized as a method of transmitting a signal in a multi-path environment. The method includes the steps of: placing a dome having a plurality of facets in the multi-path environment; transmitting the signal along a first direction in the multi-path environment with a first antenna element located on one of the facets of the dome; and transmitting the signal along a second direction in the multi-path environment with a second antenna element located on another of the facets of the dome.
A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description of the invention and accompanying drawings which set forth an illustrative embodiment in which the principles of the invention are utilized.